The present invention relates to an engine control device, and particularly to an engine control device which controls an engine having an air amount controller for controlling an intake air amount according to a target torque, and an ignition timing controller for controlling an ignition timing of an ignition system, based on an operating state of a vehicle.
Conventionally, it is known that devices which control the behavior of a vehicle to the safe side when the behavior of the vehicle becomes unstable due to a slip etc. (such as an antiskid brake system or ABS, etc.). Particularly, it is known that devices which detect a behavior such as an understeering or an oversteering occurs on the vehicle during cornering etc. of the vehicle, and give wheels a suitable deceleration so that the behavior is controlled.
Meanwhile, JP2011-088576A discloses a vehicle movement controller which adjusts a deceleration during cornering to adjust a load applied to front wheels which are steerable wheels so that a series of vehicle operator's operations (breaking, steering-in, accelerating, steering-back, etc.) during cornering of a vehicle in a normal traveling state are natural and stable, unlike the control described above for a safety improvement in the traveling state where the behavior of the vehicle becomes unstable.
Furthermore, JP2014-166014A discloses a behavior control device for a vehicle which reduces a driving force of the vehicle according to a yaw-rate related amount corresponding to an operator's steering operation (e.g., yaw acceleration) to quickly decelerate the vehicle when the operator starts the steering operation so that a sufficient load is quickly applied to the front wheels which are steerable wheels. According to this behavior control device, since a frictional force between the front wheels and the road surface increases, and a cornering force of the front wheels increases by quickly applying the load to the front wheels when the steering operation is activated, a turnability of the vehicle in an early stage of curve entry improves, and a response to the steer-in operation improves. This achieves a vehicle behavior just as the operator intended.
A control device which controls an engine in vehicles equipped with a gasoline engine determines a target torque based on an operating state of the vehicle (e.g., various operator's operations of an accelerator pedal, a brake pedal and a steering wheel, as well as a traveling environment, such as a vehicle speed, temperature, atmospheric pressure, a road slope, road surface friction coefficient). The control device then controls a throttle valve and/or a variable intake valve mechanism so that a target air amount for achieving the target torque is introduced into the engine, and controls a fuel injector so that fuel of an injection amount corresponding to the target air amount is injected.
With such an engine control device, if the behavior control device disclosed in JP2014-166014A momentarily changes the target torque in order to decelerate the vehicle according to the operator's steering operation, the throttle valve and/or the variable intake valve mechanism is controlled to achieve the change in the target torque. That is, the engine control device controls the throttle valve and/or the variable intake valve mechanism to change the air amount introduced into the engine according to the change in the target torque.
However, since a comparatively large response delay occurs by the time the control of the throttle valve and/or the variable intake valve mechanism in response to the change in the target torque is reflected to the air amount in an engine cylinder, a delay occurs in a change in an actual output torque with respect to the timing of the change in the target torque, resulting in an insufficient deceleration for the vehicle. In that case, the response to the vehicle behavior for the steer-in operation cannot fully be improved, and the vehicle behavior as the operator intended cannot be achieved.